function turnby(var xx,var yy, var r, int vv)
{
	my.y=rand()%(2*r)-r;
	my.x=sqrt(r*r-my.y*my.y);
	
	while(1)
		{
			if(my.x-xx>=0 && my.y-yy>=0)
			{
				my.x-=vv;
				my.y=yy+sqrt(r*r-pow(my.x-xx,2.0));
				}
			else if(my.x-xx<0 && my.y-yy>=0)
			{
				my.x-=vv;
				my.y=yy+sqrt(r*r-pow(my.x-xx,2.0));
				}
			}
			else if(my.x-xx<0 && my.y-yy<0)
			{
				my.x+=vv;
				my.y=yy+sqrt(r*r-pow(my.x-xx,2.0));
				}
			}
			else if(my.x-xx>=0 && my.y-yy<0)
			{
				my.x+=vv;
				my.y=yy+sqrt(r*r-pow(my.x-xx,2.0));
				}
			}
	}
